The present invention refers to plastic handles for cutting instruments such as scissors and to scissors using such handles.
It is known to manufacture scissors having steel blade members and plastic handles, for example from Brazilian patent 86447. It is also known, for example from Brazilian Utility Model patent 5500563 of Jun. 10, 1975 for dress makers scissors to have the plastic handles anatomically shaped to receive the user's fingers so as to maximise comfort and cutting control. Comfort in using the scissors depends not only on the shape but also on the extension of the surfaces of the finger-receiving holes that are contacted by the user's fingers since the sensation of effort in cutting is reduced as the area of finger contact is increased. For this reason and bearing in mind that it does not result in any appreciable increase in weight of the scissors, plastic handles may be made with shapes and sizes that are more comfortable to use and give the sensation of lightness in cutting even thick cloth.
It has been found, however, that perfect adaptability of the handles by varying their shapes and dimensions is not in practice possible due to the very variable characteristics of the hands of different individuals. An extreme example is the obvious difference between right-handed and left-handed persons.
The work "The Psychology of Everyday Things" by Donald A. Norman states: "In this case only special products help, such as scissors and knives for left-handed persons. But these special instruments sometimes do not work, for example when the same item has to be used by many different people. In such cases, the only solution is to make it ambidextrous, even if this makes it a little less efficient for each person in particular".
U.S. Pat. No. 4,091,539 to Tokuji Watanabe issued on May 30, 1978 discloses large size scissors without plastic handles but rather of a simple nature with each blade or cutting member formed with a finger-hanging hole portion by press moulding, such hole portion having then applied thereto an anatomically shaped plastic part. That patent shows how such specially shaped parts may be simply applied to the inner peripheries of the holes in the finger-hanging hole portions so as to provide inexpensive decorative large size scissors with inner protective rings in the finger holes. However, it is clearly shown that the scissors cannot be adapted for use by left-handed persons, such alternative scissors having a mirror image construction both as regards the cutting members and as regards the protective rings.
The solution of Watanabe, however, apart from not being applicable to scissors already manufactured with the larger more comfortable plastic handles, does not in any way solve the problems of variations in the characteristics of the hands of different right-handed or different left-handed people.
Other totally metallic scissors are known in which the finger holes are covered with rigid or soft plastic rings injected directly onto the metal parts or applied thereto mechanically. Examples are the products INCOLMA of Columbia (based on the product WOW ALEX of Japan), HUMMINGBIRD-PLUS of Japan, "PANDA" AMC of France, SHEFFIELD of the United Kingdom and H. W. BOKER of SOLINGEN (Germany).
Other types of scissors are known that plastic handles the "eyes" or finger holes of which are provided with hard plastic rings of different colours. Such an arrangement has a purely aesthetic purpose, an example being the product commercialised as BARRILITI by the company SOLINGEM of Germany.
Another inconvenience to be found in all known large size scissors having plastic handles and designed to be adapted specially to the hand (ergometrically designed scissors) is that, due to the bulkiness of the handles and the ergometrically formed portions of the finger holes, there is no well defined longitudinal plane of symmetry of each handle and, to the extent that such plane of symmetry could exist, it does not coincide with the cutting plane of the blade members. This makes cutting control difficult. An example can be found in the scissors commercialised by FISKARS.
A first object of the present invention is to provide a plastic handle for a cutting instrument such as scissors that automatically adjusts itself to the hand of the user, independently of the size of the hand or of whether he is right- or left-handed.